:root{
  --ink:#070710; --slab:#0e0e1a; --slab2:#13132230; --rail:#23233a;
  --paper:#e9eaf4; --dim:#9a9cb8; --ind:#6d63e8; --ind2:#818cf8; --amber:#f0b429;
  --up:#3ecf8e; --down:#f56565;
  --type:'Roboto Mono',ui-monospace,SFMono-Regular,Menlo,monospace;
  --head:'Archivo',system-ui,Segoe UI,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;color-scheme:dark}
body{margin:0;background:var(--ink);color:var(--paper);font-family:var(--type);line-height:1.66;
  -webkit-font-smoothing:antialiased;font-size:15.5px;letter-spacing:.002em}
.shell{max-width:1010px;margin:0 auto;padding:0 24px}
a{color:var(--ind2);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3{font-family:var(--head);line-height:1.12;letter-spacing:-.02em;font-weight:700}
h2{font-size:clamp(1.35rem,2.5vw,1.78rem);margin:0 0 .55em}
h3{font-size:1.04rem;margin:1.5em 0 .3em;color:#fff;font-weight:600}
.dim{color:var(--dim)}
.slab-sec{padding:46px 0}
.slab-sec + .slab-sec{border-top:1px solid var(--rail)}
.tab{font-family:var(--type);font-size:.7rem;letter-spacing:.26em;text-transform:uppercase;
  color:var(--ind2);margin-bottom:15px;font-weight:500}
/* masthead */
.bfs-bar{position:sticky;top:0;z-index:50;display:flex;align-items:center;justify-content:space-between;
  gap:20px;padding:14px 24px;background:rgba(7,7,16,.9);backdrop-filter:blur(10px);
  border-bottom:1px solid var(--rail)}
.bfs-sig{display:flex;align-items:center;gap:10px;font-family:var(--head);font-weight:700;color:#fff;
  font-size:.96rem;letter-spacing:-.02em}
.bfs-sig .dot{width:10px;height:10px;border-radius:50%;background:var(--ind);
  box-shadow:0 0 0 3px rgba(67,56,202,.28)}
.bfs-links{display:flex;gap:22px;list-style:none;margin:0;padding:0;font-size:.85rem}
.bfs-links a{color:var(--dim)}
.bfs-links a:hover{color:var(--paper);text-decoration:none}
.bfs-go{border:1px solid var(--ind);color:var(--ind2)!important;padding:7px 14px;border-radius:5px;
  font-size:.78rem;letter-spacing:.02em}
.bfs-go:hover{background:rgba(67,56,202,.16);text-decoration:none}
.bfs-burger{display:none;background:none;border:0;cursor:pointer;width:30px;height:24px;padding:0}
.bfs-burger span{display:block;height:2px;background:var(--paper);margin:5px 0;border-radius:2px}
.bfs-drawer{display:none;flex-direction:column;padding:6px 24px 18px;border-bottom:1px solid var(--rail);
  background:var(--slab)}
.bfs-drawer a{color:var(--paper);padding:10px 0;border-bottom:1px solid var(--rail);font-size:.92rem}
.bfs-drawer.open{display:flex}
/* hero + content blocks */
.bfs-lede{padding:62px 0 42px}
.over{font-family:var(--type);font-size:.72rem;letter-spacing:.22em;text-transform:uppercase;color:var(--ind2)}
.bfs-lede h1{font-size:clamp(2.05rem,4.5vw,3.05rem);margin:.34em 0 .3em;color:#fff;max-width:18ch}
.answer{font-size:1.16rem;line-height:1.55;color:#eceefc;max-width:62ch;margin:.2em 0 .9em;border-left:3px solid var(--ind);padding-left:16px}
.answer b{color:var(--ind2);font-weight:600}
.thesis{font-size:1.1rem;color:#cccee2;max-width:62ch}
.tape{display:flex;flex-wrap:wrap;gap:9px;margin-top:26px;font-size:.78rem}
.cell{border:1px solid var(--rail);background:var(--slab);border-radius:5px;padding:8px 13px;color:var(--dim)}
.cell b{color:var(--ind2);font-weight:500}
.act{display:inline-block;margin-top:28px;background:var(--ind);color:#fff;font-weight:600;
  padding:13px 22px;border-radius:6px;font-size:.86rem;letter-spacing:.02em;font-family:var(--head)}
.act:hover{background:#4f46e5;text-decoration:none}
.opener{font-size:1.04rem;color:#d6d8e8}
.slab{background:var(--slab);border:1px solid var(--rail);border-radius:10px;padding:24px 26px;margin:20px 0}
.slab.lit{border-color:#34346a;box-shadow:inset 0 0 0 1px rgba(67,56,202,.14)}
.cols{display:grid;gap:16px}
@media(min-width:720px){.c3{grid-template-columns:repeat(3,1fr)}.c2{grid-template-columns:1fr 1fr}}
.box{background:var(--slab);border:1px solid var(--rail);border-radius:9px;padding:19px}
.box h3{margin-top:0}
.mark{font-family:var(--type);font-size:.68rem;letter-spacing:.16em;text-transform:uppercase;color:var(--ind2)}
ul.book{list-style:none;padding:0;margin:16px 0}
ul.book li{padding:10px 0 10px 28px;position:relative;border-bottom:1px solid var(--rail);color:#cdcfe2}
ul.book li:before{content:"\25A0";position:absolute;left:7px;color:var(--ind);font-size:.62rem;top:14px}
.ledger{overflow-x:auto;margin:20px 0}
table{border-collapse:collapse;width:100%;font-size:.86rem;min-width:540px}
th,td{padding:12px 14px;border-bottom:1px solid var(--rail);text-align:left}
th{font-family:var(--type);font-size:.68rem;letter-spacing:.12em;text-transform:uppercase;color:var(--dim);font-weight:500}
td .gain{color:var(--up)}
.bfs-trail{font-size:.74rem;color:var(--dim);padding:18px 0 0}
.bfs-trail a{color:var(--dim)}
.bfs-trail .div{opacity:.5;margin:0 6px}
.ruling{font-size:1.06rem;color:#cccee2;max-width:64ch;margin:.45em 0 0}
.bfs-read h3{color:var(--ind2)}
.flag{font-family:var(--type);font-size:.8rem;color:var(--dim);border-left:2px solid var(--ind);
  padding:5px 0 5px 15px;margin:18px 0}
code{font-family:var(--type);background:var(--slab);border:1px solid var(--rail);border-radius:4px;
  padding:1px 6px;font-size:.84rem;color:var(--ind2);word-break:break-word}
.bfs-base{border-top:1px solid var(--rail);background:#0a0a14;margin-top:34px;padding:44px 0 32px}
.bfs-base .grid{display:grid;gap:24px}
@media(min-width:720px){.bfs-base .grid{grid-template-columns:2fr 1fr 1fr 1fr}}
.bfs-base a{color:var(--dim);display:block;padding:3px 0}
.bfs-base a:hover{color:var(--ind2)}
.bfs-base .cap{color:#fff;font-family:var(--type);font-size:.74rem;letter-spacing:.14em;text-transform:uppercase;margin-bottom:10px}
.fine{color:#6c6e8a;font-size:.8rem;margin-top:26px;border-top:1px solid var(--rail);padding-top:18px;line-height:1.7}
/* worked-proof block: a framed, numbered run-through, set apart from .flag and .slab */
.proof-steps{background:#0a0a14;border:1px solid var(--rail);border-left:3px solid var(--ind);
  border-radius:0 9px 9px 0;padding:19px 22px;margin:22px 0}
.proof-steps .mark{margin-bottom:11px}
.proof-steps ol{margin:0;padding-left:21px;counter-reset:none}
.proof-steps ol li{padding:7px 0;color:#cdcfe2}
.proof-steps ol li b{color:#fff}
.proof-steps p{margin:.6em 0}
/* schematic frame for the inline futures-desk diagrams */
figure.schematic{margin:26px 0;background:var(--slab);border:1px solid var(--rail);border-radius:10px;
  padding:20px 18px 13px}
figure.schematic svg{display:block;width:100%;height:auto;max-width:770px;margin:0 auto}
figure.schematic figcaption{font-family:var(--type);font-size:.76rem;color:var(--dim);
  text-align:center;margin-top:11px;line-height:1.55}
.sk-cell{fill:#0e0e1a;stroke:#34346a;stroke-width:1.2}
.sk-wire{stroke:var(--ind);stroke-width:1.7;fill:none}
.sk-head{font-family:'Roboto Mono',monospace;font-size:11px;fill:#fff;font-weight:600}
.sk-sub{font-family:'Roboto Mono',monospace;font-size:9.5px;fill:#9a9cb8}
.sk-axis{font-family:'Roboto Mono',monospace;font-size:10px;fill:#9a9cb8}
.sk-yes{fill:#3ecf8e;font-family:'Roboto Mono',monospace;font-size:13px;font-weight:700}
.sk-no{fill:#f56565;font-family:'Roboto Mono',monospace;font-size:13px;font-weight:700}
/* "Also read" block at the foot of a leaf or hub */
.also{margin:32px 0 0;border-top:1px solid var(--rail);padding-top:22px}
.also .cap{font-family:var(--type);font-size:.72rem;letter-spacing:.18em;text-transform:uppercase;
  color:var(--ind2);margin-bottom:13px}
.also .pair{display:grid;gap:11px}
@media(min-width:620px){.also .pair{grid-template-columns:1fr 1fr}}
.also a.tile{display:block;border:1px solid var(--rail);border-radius:8px;padding:13px 15px;
  background:var(--slab);color:var(--paper)}
.also a.tile:hover{border-color:#34346a;text-decoration:none}
.also a.tile b{color:var(--ind2);display:block;font-size:.92rem;margin-bottom:2px}
.also a.tile span{color:var(--dim);font-size:.82rem}
.gradebar{font-family:var(--type);color:var(--ind2)}
@media(max-width:719px){.bfs-links{display:none}.bfs-burger{display:block}}

/* a11y + responsive polish */
:focus-visible{outline:2px solid currentColor;outline-offset:3px;border-radius:3px}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{animation-duration:.01ms !important;transition-duration:.01ms !important}}
@media(max-width:719px){table{min-width:0}th,td{padding:8px 10px}}